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PA2AGA > HDDIG 20.06.00 03:37l 180 Lines 7349 Bytes #-9436 (0) @ EU
BID : HD_2000_169I
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Subj: HamDigitalDigest 2000/169I
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Sent: 000619/1839Z @:PI8HGL.#ZH1.NLD.EU #:53013 [Den Haag] FBB $:HD_2000_169I
From: PA2AGA@PI8HGL.#ZH1.NLD.EU
To : HDDIG@EU
Date: Mon, 19 Jun 00 17:50:56 MET
Message-Id: <hd_2000_169I>
From: pa2aga@pe1mvx.ampr.org
To: hd_broadcast@pa2aga.ampr.org
X-BBS-Msg-Type: B
their operators and power supplies ? What information is so important
that it must be transmitted coast to coast and when it finally
arrives, is it of any value anymore ?
In practice, emergency areas are of a limited geographical size and
the normal infrastructure outside this area is working. Thus, it is
sufficient to get a connection from the emergency area to the outside
world. Emergency areas are seldom larger than the VHF/UHF range from a
well located analog or digital repeater, which must have emergency
power available. Even better is a mobile repeater or BBS station,
which can be driven to good place and operating as long as there is
gas in the tank. This can then work with portable stations in the
emergency area and also connection to stations outside emergency area,
which have working land line connections.
Such a mobile store and forward station is also very valuable for
search and rescue operations in the wilderness, since portable
stations can try to get contact to base station when they are at good
locations and thus save battery power, which is a scarce resource when
operating portable.
You think it is a bad thing that amateur stations connected to land
lines, are a work around bulletin forwarding networks eating up all
the traffic, but from _emergency_ communication point of view I think
it is better to think that individual radio links are work arounds for
faulty land line links. Of course, this requires that the traffic can
be limited to emergency traffic on the narrow radio channel. Part of
the emergency drill should be putting up a connection from the land
line environment to the radio environment, setting up the filtering
etc. A well located node or preferably digital repeater will extend
the communication range greatly. I do not see a need for store and
forward capability, unless the stations have an intermittent (e.g.
dial-up) connection to the land line network.
Paul OH3LWR
------------------------------
Date: Sat, 17 Jun 2000 19:28:43 +0200
From: "." <italy99@tin.it>
Subject: OM Internet Site
http://216.121.96.176/euroww/radioamatori
------------------------------
Date: Sun, 18 Jun 2000 12:43:32 +1000
From: "David Findlay" <nedz@bigpond.com>
Subject: Packet Radio
> But then you rely on everyone's capability to hear another. That will be
a
> costly mistake, that you will only discover when you are beyond the stage
> of initial experiments...
If someone couldn't hear repeaters would be required. Some of the stations
could be configured to do this on a slightly different channel.
> Few people have the motivation to document a failure.
How are people supposed to learn from the failure of others then?
> The only problem is that your system does not work in practice.
> It is re-invented every decade, and people try to set it up only to
> discover that it starts to break down once the usage of the channel gets
> beyond a certain level, and the number of stations that do not hear
another
> (and thus happily transmit at the same time) goes up.
You would have to have a grid of areas. Each grid square uses a single
channel. To get to stations beyond your square you use a gateway that sits
in both channels. The limit per channel would have to be around 50 users.
> The current breed of packeteers that is wandering into this trap is using
a
> mode called APRS. From what I understand about your intentions, you
should
> just drop your datarate expectations to 1200 or 9600 bps and dive into the
> APRS thing. It works the way you think a network can work, and you will
> quickly see what the limitations are.
Anyone got a URL for APRS?
> Only it does not use established network protocols like IP (with
> multicasting), but it builds on the amateur packet protocol AX.25 in
> datagram mode, with an ad-hoc definition of datagram contents.
> (position reports, weather reports, short messages, etc)
After some thinking I now realize that TCP/IP would be no good. It would
have to use a protocol with the same versatility but adapted to take into
account limitations of the amateur radio system. But the thing that I think
is really important is not using a single system for all hams. What needs to
happen is that all systems are linked into one larger network. The internet
is a collection of heaps of different styles of networks, but they all work
nicely together. To do the same with packet radio would require the setup of
gateways between different types of networks.
David Findlay
------------------------------
Date: Sun, 18 Jun 2000 09:24:21 GMT
From: nomail@rob.knoware.nl (Rob Janssen)
Subject: Packet Radio
David Findlay <nedz@bigpond.com> wrote:
>> But then you rely on everyone's capability to hear another. That will be
>a
>> costly mistake, that you will only discover when you are beyond the stage
>> of initial experiments...
>If someone couldn't hear repeaters would be required. Some of the stations
>could be configured to do this on a slightly different channel.
Then you will have to link the repeaters.
>> Few people have the motivation to document a failure.
>How are people supposed to learn from the failure of others then?
The failures I am talking about are not technical failures, but failure
to keep enough commitment to the project. When the commitment is lost,
there usually is nobody who wants to write an article about that.
>> The only problem is that your system does not work in practice.
>> It is re-invented every decade, and people try to set it up only to
>> discover that it starts to break down once the usage of the channel gets
>> beyond a certain level, and the number of stations that do not hear
>another
>> (and thus happily transmit at the same time) goes up.
>You would have to have a grid of areas. Each grid square uses a single
>channel. To get to stations beyond your square you use a gateway that sits
>in both channels. The limit per channel would have to be around 50 users.
This is the system that we have been trying to setup. Of course you do
not want to pollute your square with transmissions from a strong station
in the next square, so you use a separate frequency to link the squares.
The problem with this approach is that the integrity of your entire network
depends on the availability of the repeaters and their links. Once
repeaters start going down because of lack of commitment, your whole
network quickly falls apart.
>Anyone got a URL for APRS?
Use any search engine.
>But the thing that I think
>is really important is not using a single system for all hams. What needs to
>happen is that all systems are linked into one larger network. The internet
>is a collection of heaps of different styles of networks, but they all work
>nicely together. To do the same with packet radio would require the setup of
>gateways between different types of networks.
Stop dreaming - this is not going to happen. The world is too large to be
covered by amateur packet radio networks like it has been covered by the
Internet.
(the software that is in use mostly could do it, but the hardware simply
isn't in place and will never be)
Rob
To be continued in digest: hd_2000_169J
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